[cmake] Call FindMETIS from FindParMETIS

Thanks to Simon Praetorius for providing the patch idea.

changed milestone to %DUNE 2.7.0

added bug label

mentioned in merge request dune-grid!355 (merged)

added 1 commit

• 746e8821 - [bugfix][cmake] Don't abort cmake config when METIS is not found.

Compare with previous version

The problem @robert.kloefkorn pointed out in dune-grid!355 (merged) is probably that on some systems you can install ParMETIS without installing METIS separately. Then you need to search for metis.h in the ParMETIS directory and not only in the METIS directory (what is done by FindMETIS.cmake. A solution could be to add additional search directories to find_file or find_library when find_package(METIS) is called inside FindParMETIS.cmake, or maybe one can set

if(NOT METIS_DIR)
  set(METIS_DIR ${PARMETIS_DIR})
endif(NOT METIS_DIR)

or something similar, before calling find_package(METIS).

@simon.praetorius Such ParMETIS installations exist? Your idea seems to be right. Can you provide a merge request and assign it to me? I'll merge this nevertheless because I hope to fix the code I broke.

This is not a valid parameter for fphsa. FAIL_MESSAGE only indicates the error message, not how to handle the problem.

What about including the variable METIS_FOUND in the find_package_handle_standard_args function in line 121?

changed this line in version 3 of the diff

An example installation of ParMETIS in non-system location is a download-all installation of PETSc. There, all includes are in the same directory and also all libraries. So, if you specify PARMETIS_DIR=PETSC_DIR but not METIS_DIR, METIS is not found.

In the old FindParMETIS.cmake there was a comment, that there is an "installation bug in ParMETIS 4.0.3" that forces you to "copy [metis.h] manually next to parmetis.h", because CMAKE_REQUIRED_INCLUDES was set to PARMETIS_INCLUDE_DIR. But, when METIS_FOUND was already true before, maybe the search was skipped completly(?)

Tree solutions:

1. If you want to use ParMETIS, your also have to specify METIS_DIR
2. We set additional search PATHS or HINTS to find_path and find_library in FindMETIS.cmake depending on PARMETIS_DIR
3. We set METIS_DIR to PARMETIS_DIR in case the former is not defined and with this adjust the search paths.

I merge this without the patch from Robert. If this does not solve all problems, please let me know and we discuss further issues.

enabled an automatic merge when the pipeline for d85085a0 succeeds

merged

mentioned in commit 6f0293eb

@gruenich: Your patch still breaks my tool chain. I'm tending to revert all the related patches since it seems impossible to implement a decent fix.

@gruenich: I fixed your stuff in !714 (merged) and now stay away from quick cmake fixes plz. Obviously, the test suite for cmake is not sufficient to just run it in the CI. It needs to be fixed because changes in dune-common can affect a lot of down stream modules. And there is a quite a number of different combinations that need to be checked. I doubt that you have done that nor that you have the time for it.